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Thenumber of common tangents to the circles `"x"^("2")"+y"^("2")"-4x-6y-12=0"`and `x^2+""y^2+""6x""+""18 y""+""26""=""0`,is :(1)1 (2) 2 (3) 3 (4) 4 |
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Answer» `x^2 + y^2 - 4x - 6y - 12= 0` `x^2 - 4x + 4 + y^2 - 6y+ 9 - 12 - 4 - 9 = 0` `(x-2)^2 + (y-3)^2 = 25= 5^2` `c_1 = (2,3) & r_1= 5` `x^2 + y^2 + 6x + 18y + 26= 0` `x^2 + 6x + 9 + y^2 + 18y + 81 + 26 - 9 - 81= 0` `(x+3)^2 + (y+9)^2 = 64= 8^2` `c_2 = (-3,-9) & r_2= 8` `c_1 = (2,3); r_1=5` `c_2 = (-3,-9) ; r_2= 8` `d(c_1,c_2) = sqrt((2- (-3))^2 + (3- (-9))^2` `= sqrt(25 + 144) = sqrt(169)= 13` `r_1 = 5 ; r_2= 8` `r_1 + r_2 = 13` so,`3 `tangents option 2 is correct |
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